Asymmetric Iminium Ion Catalysis: An Efficient Enantioselective Synthesis of Pyranonaphthoquinones and β‐Lapachones

An addition–cyclization reaction cascade triggered by an organocatalyst was used for the enantioselective preparation of a series of biologically active 1,2‐ and 1,4‐pyranonaphthoquinones from aliphatic and aromatic α,β‐unsaturated aldehydes and 2‐hydroxy‐1‐4‐naphthoquinone. A trimethylsilyl‐protected diarylprolinol serves as the Lewis base organocatalyst.